Many electronic devices may include a touch-sensitive surface for receiving user input. Example devices which may benefit from a touch sensitive surface may include cellular telephones, smart phones, personal digital assistants, tablet computers, laptop computers, track pads, wearable devices, health devices, sports accessory devices, peripheral input devices, and so on.
The touch-sensitive surface may detect and relay the location of one or more user touches (e.g., have multi-touch sensing functionality) which may be interpreted by the electronic device as a command or a gesture. In one example, the touch input may be used to interact with a graphical user interface. Despite many advantages, touch sensitive surfaces are generally limited to providing only the location and/or area of the one or more touch events.
However, many materials used with force sensitive surfaces expand and/or contract with changes in temperature. For example, a user's finger can locally increase the temperature of the area that user is touching. In other cases, ambient temperature and/or internal heat-producing components can cause a temperature gradient through the electronic device.
Undesirably, such temperature changes can cause the strain-sensitive surfaces to either expand or contract, which in turn may place the surface under stress and/or strain. In these cases, temperature changes can be registered by the strain-sensitive surface as a force input. In other examples, forces registered from temperature effects can obscure or conceal actual force input from a user, or register as false positives for force inputs.
Accordingly, there may be a present need for an improved force-input surface capable to detect and relay the force applied at one or more user touch locations, while effectively compensating for effects of temperature.